The invention relates to a magnetic head for use in vertical recording having a magnetic pole in the form of a thin film of a soft magnetic material and a body constituted by two protective blocks and having a contact surface to mate with a magnetic recording medium. The magnetic pole is enclosed between the protective blocks and extends up to the contact surface, at least one of the protective blocks having a first magnetic portion and a second portion distinct therefrom a winding aperture provided in the first portion causes a flux collect part present between the magnetic pole and the winding aperture and a flux return part to be separated. The second portion extends between the first portion and the contact surface and constitutes a boundary for the winding aperture. At least a winding is wound around at least the magnetic pole and the flux collect part through the winding aperture. A magnetic head of this type is known from European Patent Application EP No. 0,199,422 to which U.S. application Ser. No. 854,209 corresponds, herewith incorporated by reference).
In the art of short-wavelength magnetic recording it is known that vertical recording, that is to say recording in which the magnetisation in the magnetic layer of the recording medium is effected in a direction at right angles to the direction of movement of the recording medium and at right angles to the surface of the medium, is more favourable than recording in the longitudinal direction in which magnetisation is effected in the direction of movement of the recording medium. A reason for the effect is that the demagnetising field within the magnetic layer of the recording medium increases as the wavelength decreases in the case of recording in the longitudinal direction, whereas the demagnetising field decreases in the case of vertical recording. The recording medium may be in the form of a tape and it may consist of a support on which a soft magnetic layer and a recording layer are provided.
In vertical recording it is important that the main component of the magnetic field coming from the magnetic head is perpendicular to the magnetic recording medium as much as possible. The said known magnetic head has this property.
In the known magnetic head one of the protective blocks is entirely formed from a non-magnetic material and the other protective block is composed of two separate sub-blocks, a first sub-block of which is magnetic and a second is non-magnetic. The second sub-block extends from the bonding surface between the two sub-blocks up to the contact surface of the magnetic head. A groove extending up to the bonding surface and constituting the winding aperture is provided in the first sub-block. The magnetic pole is provided against the protective block formed from the non-magnetic material.
Technologically, the known magnetic head has the drawback that expensive and time-consuming extra polishing steps have to be performed during the manufacture of the magnetic head. This is due to the fact that one of the protective blocks is composed of two different materials so that a satisfactory bonding between the sub-blocks of the relevant protective block can only be ensured if the two sub-blocks, prior to their being joined at the bonding surface have a very satisfactory flatness and smoothness.
It is to be noted that a magnetic head for vertical recording is known from British Patent Application GB No. 2,126,408 in which each of the protective blocks is composed of a first magnetic sub-block and a second non-magnetic sub-block secured to the first block. In addition to the above-mentioned drawback, this known magnetic head has the further drawback that the magnetic pole in the form of a thin film is provided on one of the composite protective blocks. In fact, it is very difficult during manufacture of the magnetic head to get a completely smooth and flat side-face, generally a sawn face, of such a composite protective block. This is because the polishing process is not necessarily optimized for the different materials of the first and second sub-blocks so that a step and/or a crack can sometimes by measured in the surface after the polishing process. This may cause an interrupted pole if the thin film is provided on such a polished sideface.